Process for vulcanizing polychloroprene



Patented Feb. 23, 1954 UNITED STATES PATENT OFFICE PROCESS FOR VULCANIZING POLYCHLORQPRENE John J. Verbanc, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Application February 7, 1952, Serial No. 270,503

6 Claims.

. erators.

The polychloroprenes to which the present invention relates are those compounds commonly known in commerce as neoprene. Neoprene is a generic name applied to the polymers of chloro-l,3-butadiene (chloroprene), and to copolymers of the same with diene or vinyl compounds such as acrylonitrile, butadiene, isoprene, dichlorobutadiene, and styrene, in which copolymers the chloroprene is the predominant monomer. These polymers (which term is used to include copolymers) may be made in aqueous emulsions and are available today under such names as Neoprene Type GN, Neoprene Type W,. Neoprene Type FR, and as latices under type numbers such as Type 571, Type 735, and Type 842, all of which are generally referred to as polychloroprenes or chloroprene polymers.

Polychloroprenes differ greatly from other synthetic rubbers and from natural rubber in the manner in which they can be vulcanized. With most types of polychloroprene, good vulcanizates may be obtained by incorporating certain metal oxides in the plastic polymer and heatin to effect vulcanization. However, it is customary to use in conjunction with the metal oxides certain organic accelerators which increase the rate of cure and improve vulcanizate properties. With some'types of polychloroprene, such as those made in the presence of aliphatic mercaptans, metal oxides act slowly and do not produce a high state of cure everr after long periods of heating. With polychloroprenes of this type, accelerators are necessary for a good cure.

Among the polychloroprene accelerators in current use may be mentioned NA-22 (ethylene thiourea which may also be referredto as 2-mercaptoimidazoline) and Permalux tolylguanidine salt of dicatechol borate). These accelerators, which are in general use on the market today, produce excellent polychloroprene vulcanizates but, because theyare so active at (the di-O- canization temperatures but provide a much wider margin of processing safety than do the accelerators currently used.

I have found that a limited class of compounds prepared by the Mannich reaction, which will be hereinafter referred to as Mannich bases, materially increase the speed of vulcanization of polychloroprene but present less hazard with reard to scorching than do the vulcanization accelerators that are now being used with polychloroprene. The Mannich bases employed in the process of the present invention are those prepared from phenols and naphthols which contain one to three 'dimethylaminomethyl groups in the positions ortho and para to the hydroxy radical. The phenolic and naphtholic Mannich bases employed in this invention may contain in addition to the dimethylaminomethyl groups one or more substituents in the aromatic ring or rings. These substituents may be alkyl, aralkyl, aryl, alkoxyl, aralkoxyl, amino, alkylamino, acylamido, nitro, halogen or carboxyl groups, the hydrocarbon radicals of such groups when present containing not more than 8 carbon atoms. Although a large number of these phenolic and naphtholic Mannich bases containing a wide variety of substituents have been used, no substituted phenolic or naphtholic Mannich bases have been found which do not exhibit the accelerating effect in the vulcanization of polychloroprene.

The preferred phenolic and naphtholic Mannich bases for use in the present invention are those which contain at least two dimethylrelatively low temperatures, care must be exwh ch accelerators are active at ordinary vu'1- I aminomethyl groups. The metal salts of these phenolic and naphtholic Mannich bases, and more particularly the light metal salts (those having a density of less than 4, such as Na, K, Ca, Mg and Al) exhibit a high order of acceleratin activity and also good scorch-resistance characteristics.

In general the accelerators of this invention are used with from 1% to 8% or more of zinc oxide and preferably also with from 1% to 8% or more of magnesium or other metallic oxide. The Mannich bases are preferably used in an amount of about 0.5% to 3.0% and in general suitable curing temperatures will be found to be between and 205 C. The percentages mentioned above are based on the weight of the polychloroprene. Although the aromatic Mannich bases as above described show activity in the various types of polychloroprene, their use is of particular value with chloroprene polymers which have been produced in the presence of aliphatic mercaptans by processes such as described in U. S; Patent 2,494,087, U. S. Patent 2,573,009, etc.

The following examples are given to illustrate the invention. Parts are given by Weight unless otherwisespecified.

Example 1 Polychloroprene was compounded according to the following formula:

TrParts Polychloroprene 1 100 Phenyl-alpha-naphthylamine 2 Semi-reinforcing furnace ca'rbonzblack-.. 1:29

1. Unacoelerated control 2. Ethylene thiourea 3. 2,4- di(dimethylaminomethyl) 6 --methylphenol 4. 2,4,6-tri(dimethylaminomethyl) phenol 5. 2,6-di(dimethylaminomethyl) phenol 6. di (dimethylaminomethyl) -3 -methylphenol 7. 2,6--di(dimethylaminomethyl) 4 methylphenol sponding unaccelerated stock. A positive value indicates an increase in minutes in safety over the-1 time requiredfor the unaoceleratedfiicontrol. Reference data afor the i compounds tested by this method are provided in Tables II to IX.

TABLE II Stress in p. s. l. at

300% Elonga- I tlon, Cure at 153 Delta -"Aceeleretor (Parts) Mill Scorch 20 Min. 40 Min.

-None 1, 250 1, 400 0 "Ethylene thiourea (0.5) 2, 500 3,150 2,4 di (dimethylamincmethyh- 6 methylphen'ol (1.0) -1 2, 130 3, 180 +3 Table III shows data for substituted -2' ,4, 6-tri- (dimethylaminomethyl) phenols. See Table II for control.

-'1ABLE- Ii V Stressin p; s. i." at z 300% zElongaa tlon, Cure at 153? Delta Substituent C. Mill .=Scor'eh Table IV. -shows data for substituted 2;6-"diCdi- .TABLE- I M-in' 1 2 3 4 5 6 7 Cure 1 3 0.5) 1.0 (2.0 1.0a (1L0) (I10) (1.0 par part parts, pa'rt part part part v 1 -l0 1 275' l, 525 1, 525 l, 700 1, 370 1' 450 1,550 "0. 0 .1 m at 300% 850 1, 750 1, 775 1. 725 2, 000 1: 900 1, s50 0 800 1,900 2, 0.50 1, 775 2,200 2.100 2,075 1, 000 I -10 1,600 3, 875 3, 900 3, 575 3, 625, 3, 825 3, 500 ,3, 575 Tensile-strength in p. S. 1. 20, 3, 100 3, 875 3, 675 3, 600 3, G25. 3, 925 3, 600 3, 875 v '40 3,000 3, 600 3,700 3, 775 3, 700 3, 850 3, 525 3,800 Percent CompressionSet (70 7 Hnat 100 O.) 25 63 22-25 21 11 -25 30, 37 Yerzl'ey Resilience (percent)- "25 66 75 75 77 77- 76 7 5 Mooney scoreml lvlin. for 10' 1 5 J j point riseabove minimum. v

'value (l2l O.) 11' '27 23 25 '32 '32 27 1 Equal to ethylene thiourea in test at 70 C. for 22 hours.

Table 1 illustrates that various phenolic Mannich bases produce a state of cure equivalent to that from ethylene thiourea. However, an-outstanding advantageobtained-with these phenolic-Mannichbases is the'large increasein processingsafety as; evidenced by the .Mooneyscorch values.

1 Example 2 'The following ingredients 1 wereused in oampounding:

" Unless otherwiseindicated in thefollowing tables.

Small ring specimens were 'cured an'd' th'en tested in water at 25 C. bymeans of the Williams tensile "machine [see Williams andSturgisQInd. Eng; Chem, 31,1303 (1939) l. The scorchiness" of therawstock was determined bye-mill scorch test. In this test *z l grams of-compoun'ded raw stock ismilledon a- 2 :x 6' mill held at 135 C. with an opening of 0.016 inch. The endpointoi the test (occurs at that time when the stock for at least one-half the roll width becomes alacy and refuses eto band. This is known as the scorch: time. The longer the scorch time, the less scorchy is the stock. fDeltaMi-ll Scorch is the diiierencein' minutes 'betweenathamill scorch time of an accelerated stock and that of a corremethylaminomethyl) :phe'nols. cSee Table ILitor control.

1 i able (V shows data for substituted'ze-idimethylaminomethyl phenols.

TABLE v methylaminomethyl) -'-6-methyl phenol are shown in Table IX. See Table II for control.

Stress in p. s. l. at TABLE IX ti e i g D it on urea G a Substituent o. Min ggggj fig- 1 g? Metal Derivative of 2,4'di(dimethyl- Rig,- 20 Min 40 Min. aminomethyD-B-methyl phenol Scorch 1'62" 1,730 +3 20 Min. 40 Min. 12:3 its a: I

I Sodium ,910 2, 730 +1s+ Egg 1? Magnesium 1, 900 2. 980 +6 Aluminum 2, 330 2,390 +3 -n-bntylamino 2, 220 2, 810 3 Example 3 l5 The vulcan1zat1on of a polychloroprene gum Table VI contains additional examples. See stock with 2,4 dudimethygaminomethyp Table V for control methyl phenol was carried out with the following formulation: TABLE VI 20 Parts t Polychloroprene (as in Ex. 1) 100 533:? igfigg l Phenyl-alpha-naphthylamine 2 ti0n, ureatl53 1 Extra light calcined magnesia 2 Accelerator 0- Scorch ii fyirlp h 5 cce era or as own. Min. 40 Min. S

Test results are summanzed in Table X. Slabs 2,2-di[3.5'-di(dimethylaminomethyD- and pellets were cured and tested by standard 4-hydroxyphenyl] propane 1,790 2,870 +21 A S T M th d 2.5-di (dimethylaminomethyl) hydroquinone 1,650 3, 040 +10 7 TABLE x 4 (or 6) dimet methyl phenol l, 480 2, 190 +5+ 4- dimethy1aminomethyl-2-methyl- 2,4-di (difi-chlorophenol 1,730 1, 360 +6 Mm Ethylene g g g Cure at 'Ihlourea methy1)-6- 153 0. mfithyll- Mannich bases from resorcinol were prepared 3? by reaction with varying proportions of formaldehyde and dimethylamine. An example of such 10 1 100 0 St essin .s. t600 e1 11 at on. a preparation 1s presented in Table VII. This p 1 32 resorcinol Mannich base Was obtained by reac- TwSfleSt'engthmP-S- 21 600 31325 tion of resorcinol, formaldehyde and dimethyl- 4Q f figg g Set (701% 25 35 27 amine in the ratio 0.4/0.88/0.88 at 25 to 30 C. ernit r esni'gc'e' fifi'cii 25 81 a0 ooney corc in. or 10 oin for three hours. The product was isolated by rise above v iue fm ether extraction. 0. I is 36 TABLE VII 4 Stressin slat The vulcanization of a polychloroprene clay som 1210;1 Mill stock with 2,4 di(dimethylaminomethyl) 6 on, urea corc v Accelerator (Parts) Q in Mm methyl phenol was carried out with the follow 1 1 8t mg formulation: 20 Min. 40 Min. Parts Polychloroprene (as in Ex. 1) 100 Unaeceiemted 1,250 1,400 as Phenyl-a1Pha-naphthy1am1ne 2 Resoreinol Mannlch has 2. 330 3, 010 22 Crown clay- 29 Ethylene thlollrefl 2,500 3,150 Extra light calcined magnesia 2 Zinc Oxide 5 Accelerator as shown. Test results for Mannich bases derived from naphthols are given in Table 111 s m Test results are summanzed in Table XI. Slabs VII for controL and pellets were cured and tested by standard A. S. T. M. methods. TABLE VIII TABLE x1 stsrgg syin tale. 1. at -36 ongaiion'fcure at 153 Delta g yle e 2 Accelerator 0. Mill ur ecat ouree met y)-6- Scorch 35 153 (0.5) 11522 1 20 Min. 40 Min. (1.0)

l-dimeth laminomethyl-Z-naphthoL. 1,620 2,160 2 20 1,775 1.950 2-dimethglaminomethyl-l-naphthoL. 1,3110 1,090 -e stressinp S i 600% 3g 3g 3.3%) In Tensile strength in p. s. i 40 3:825 4:100 Percent Compression Set hrs. at 0. 25 41 40 Metal derivatives of phenolic Mannich bases fil 25 79 76 produce a high state of cure while retaining good 333% 532;; 1 3 gg f safety. Results of tests with the sodium, mag- 13 1 nesium and aluminum derivatives of 2,4-di(di- 15 eagmcssaa mzampiafi Polychloropre'ne "prepared by "the process "of U. S. Patent 2,234,215, usingtetramethyl thiuram disulfide, was compounded according to the following'iormnla. BSlabs and pellets of the polymer were a cure'deand"tested.byestandandeA S. TnM.

methods. The vtesting -resu1ts -'-are=shown in Table-XII.

Parts T0 *Elychloroprene 3200 Phenylbetamaphthylaniine .1 Stearicacid 4.0.5

Extra light calcined magnesia 4 nsembreinforcing furnacecarbonblack--- .529 1'5 fZinc. oxid 15 .iAccelerator.LasJistdiAnEabIeiXlII). 1L5

TABLE XII I V methyl- 835a $21 s e m 153 6. orator Thoma phenol 4 P895 1 675 25 Bt-res'srin 191s. i;.at300%1{ F 5 z 1:875 t. .160 1; 00 2, 200 1, Tensile strength in p. i 1 so as, 400 a, 27s 3, 400 Percent rcompression Set (70 hrs. at 70 0.). 20 s1 48 49 Yeifley ResiIience (percent) 20 73. 5 1s. 0 75 4 Mooney: sc0rch;tzmin; ipi'llnpoint rise above minimum valnc' tl2l? I claim:

.1. lhe process of yuleanizing chloroprene polymerswhichccmprises incorporating in the chloroprenegpolymer stock, containing at least 1% of zinc oxide; from"'0'.5% to 3.0% of-aa-Mannich base ofthegroup consistisng of phenols and naphthols containing from one to three dimethylamino- .methyLgroups and heatingat yulcanizing stemperatnres to sefieet curing of thepolymer.

2. Theprocess of vulcanizing chloro-prenepolymers which comprises incorporating in the chloroprene: polymer stock, containing atleast 1"%*0'f zinc oxide, from- 0.5 to3.0 of '2,'4-"di ('dimethylaminomethyl) e6-methyl, phenoL. and heatin giat vulcanizing temperatures to efiect curing of the p lymer.

3. The process of vulcanizing;enloroprenepolymers which comprises incorporating in the chloroprene polymer stock; containing at least 1% of methylaminomethyl) phenol, and heating at vulcanizing temperatures to effect curing of the polymer.

4. Annnvulcanized chloropren polymer which can be rapidly. cured at ordinary vulcanizing temperatures, "containing -from'0:5% -to 3. 0% --of--a Mannich base of the groupxconsisting of phenols and naphtho'lscontaining from :one'to threeidimethyl aminomethyligroups.

5. An ,unvulcanized chloroprene polymerwhich can be rapidly cured -ordinary :vulcaniz'ing temperatures, containing from"0;5% "t03'.0% of 214-111(dimethylaminomethyl) =6'-methyl phenol.

6. An unvulcanized ehloroprene polymer which can'be'rapidly curedaterdinary'vulcanizingtemperatnrea. containing from 025%. to 3L0 %-*of"2,'4,'6- trifiidimethylaminomethyl) phenol.

JOHN JfvERBANC.

Name JDate Alexander May 17, 1938 Number 

1. THE PROCESS OF VULCANIZING CHLOROPRENE POLYMERS WHICH COMPRISES INCORPORATING IN THE CHLOROPRENE POLYMER STOCK, CONTAINIG AT LEAST 1% OF ZINC OXIDE, FROM 0.5% TO 3.0% OF A MANNICH BASE OF THE GROUP CONSISTING OF PHENOLS AND NAPHTHOLS CONTAINING FROM ONE TO THREE DIMETHYLAMINOMETHYL GROUPS, AND HEATING AT VULCANIZING TEMPERATURES TO EFFECT CURING OF THE POLYMER. 